1. Field of the Invention
The present invention is related to the noninvasive measurement and monitoring of the absolute value of intracranial pressure.
2. Prior Art
Intracranial pressure (ICP) is closely related to cerebral blood flow (CBF). To a first approximation, CBF is determined by the cerebral perfusion pressure (CPP). CPP is the difference between arterial blood pressure (BP) and intracranial pressure (ICP). Thus CPP=BP−ICP. Increase in ICP results in smaller values of CPP and CBF. Because of the difficulty of measuring CBF directly, BP and ICP are often measured to assess CPP. In a healthy individual, automatic regulation mechanisms in the body keep BP, ICP, and cerebral vascular resistance within a normal range and CBF is closely matched to the brain metabolic needs. These automatic regulation systems are often non-functional in brain trauma, stroke, hydrocephalic patients, and patients with liver or kidney failure, so that monitoring and management of ICP becomes a critical aspect of medical care. ICP>20 mmHg is recommended threshold for treatment in trauma patients (J Neurotrauma 2007; 24 Suppl 1:S55-8).
Current ICP monitoring techniques are generally grouped as either invasive or non-invasive.